224 lines
7.3 KiB
HTML
224 lines
7.3 KiB
HTML
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original version by: Nikos Drakos, CBLU, University of Leeds
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* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan
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* with significant contributions from:
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<H2><A ID="SECTION00665000000000000000">
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Overlapping sample looper</A>
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</H2>
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<A ID="sect2.example.overlap"></A>
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<P>
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As described in Section <A HREF="node29.html#sect2.enveloping">2.3</A>, it is sometimes desirable to
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use two or more overlapping looping samplers to produce a reasonably continuous
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sound without having to envelope too sharply at the ends of the loop. This is
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especially likely in situations where the chunk that is looped is short,
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a tenth of a second or less. Example B10.sampler.overlap.pd, shown in Figure <A HREF="#fig02.16">2.16</A>
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(part a), realizes two looping samplers a half-cycle out of phase from each
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other. New object classes are:
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<P>
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<DIV ALIGN="CENTER"><A ID="fig02.16"></A><A ID="2466"></A>
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<TABLE>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure 2.16:</STRONG>
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(a) two overlapped looping samplers (B10.sampler.overlap.pd); (b) the
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same, but with a phasor-controlled read point (B11.sampler.rockafella.pd).</CAPTION>
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<TR><TD><IMG
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WIDTH="617" HEIGHT="741" BORDER="0"
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SRC="img285.png"
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ALT="\begin{figure}\psfig{file=figs/fig02.16.ps}\end{figure}"></TD></TR>
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</TABLE>
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</DIV>
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<P>
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<BR><!-- MATH
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$\fbox{ $\mathrm{loadbang}$\ }$
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-->
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<IMG
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WIDTH="87" HEIGHT="41" ALIGN="MIDDLE" BORDER="0"
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SRC="img286.png"
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ALT="\fbox{ $\mathrm{loadbang}$\ }">:
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<A ID="2561"></A>output a "bang" message on load. This is used in this patch to make sure the
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division of transposition by chunk size will have a valid transposition factor
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in case "chunk size" is moused on first.
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<P>
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<BR><!-- MATH
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$\fbox{ $\mathrm{expr}$\ }$
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-->
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<IMG
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WIDTH="55" HEIGHT="33" ALIGN="MIDDLE" BORDER="0"
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SRC="img287.png"
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ALT="\fbox{ $\mathrm{expr}$\ }">:
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<A ID="2562"></A>evaluate mathematical expressions. Variables appear as $f1, $f2, and so on,
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corresponding to the object's inlets. Arithmetic operations are allowed,
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with parentheses for grouping, and many library functions are supplied,
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such as exponentiation, which shows up in this example as "pow" (the
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power function).
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<P>
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<BR><!-- MATH
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$\fbox{$\mathrm{wrap}\sim$}$
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-->
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<IMG
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WIDTH="65" HEIGHT="33" ALIGN="MIDDLE" BORDER="0"
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SRC="img288.png"
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ALT="\fbox{$\mathrm{wrap}\sim$}">:
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<A ID="2563"></A>wrap to the interval from 0 to 1. So, for instance, 1.2 becomes 0.2; 0.5
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remains unchanged; and -0.6 goes to 0.4.
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<P>
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<BR><!-- MATH
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$\fbox{ $\mathrm{send}\sim$\ }$
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-->
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<IMG
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WIDTH="72" HEIGHT="41" ALIGN="MIDDLE" BORDER="0"
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SRC="img289.png"
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ALT="\fbox{ $\mathrm{send}\sim$\ }">,
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<!-- MATH
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$\fbox{ $\mathrm{s}\sim$\ }$
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-->
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<IMG
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WIDTH="48" HEIGHT="33" ALIGN="MIDDLE" BORDER="0"
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SRC="img290.png"
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ALT="\fbox{ $\mathrm{s}\sim$\ }">,
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<!-- MATH
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$\fbox{ $\mathrm{receive}\sim$\ }$
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-->
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<IMG
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WIDTH="88" HEIGHT="40" ALIGN="MIDDLE" BORDER="0"
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SRC="img291.png"
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ALT="\fbox{ $\mathrm{receive}\sim$\ }">,
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<!-- MATH
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$\fbox{ $\mathrm{r}\sim$\ }$
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-->
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<IMG
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WIDTH="47" HEIGHT="33" ALIGN="MIDDLE" BORDER="0"
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SRC="img292.png"
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ALT="\fbox{ $\mathrm{r}\sim$\ }">:
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<A ID="2564"></A><A ID="2565"></A><A ID="2566"></A><A ID="2567"></A>signal versions of <TT>send</TT> and <TT>receive</TT>. An audio
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signal sent to a <TT>send~</TT> object appears at the outlets of any and
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all <TT>receive~</TT> objects of the same name. Unlike
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<TT>send</TT> and <TT>receive</TT>, you may not have more than one
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<TT>send~</TT> object with the same name (in that connection, see
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the <TT>throw~</TT> and <TT>catch~</TT> objects).
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<P>
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In the example, part of the wavetable reading machinery is duplicated, using
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identical calculations of "chunk-size-samples" (a message stream) and
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"read-pt" (an audio signal smoothed as before). However, the "phase"
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audio signal, in the other copy, is replaced by "phase2". The top part
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of the figure shows the calculation of the two phase signals: the first one
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as the output of a <TT>phasor~</TT> object, and the second by adding
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0.5 and wrapping, thereby adding 0.5 cycles (<IMG
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WIDTH="13" HEIGHT="13" ALIGN="BOTTOM" BORDER="0"
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SRC="img41.png"
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ALT="$\pi $"> radians) to the
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phase. The two phase signals are each used, with the same range adjustments as
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before, to calculate indices into the wavetable and the <TT>cos~</TT> object, and to control the two <TT>samphold~</TT> objects. Finally, the
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results of the two copies are added for output.
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<P>
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<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
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SRC="index.png"></A>
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<BR>
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<B> Next:</B> <A ID="tex2html1093"
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HREF="node38.html">Automatic read point precession</A>
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<B> Up:</B> <A ID="tex2html1087"
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HREF="node32.html">Examples</A>
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<B> Previous:</B> <A ID="tex2html1081"
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HREF="node36.html">Looping samplers</A>
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<B> <A ID="tex2html1089"
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HREF="node4.html">Contents</A></B>
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<B> <A ID="tex2html1091"
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HREF="node201.html">Index</A></B>
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<ADDRESS>
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Miller Puckette
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2006-12-30
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